(CNN) -- Investigators said Tuesday they did not yet know the cause of a fire that extensively damaged a women's clinic in Pensacola, Florida.
A prompt response Sunday morning by fire crews "preserved enough of the building to take evidence from," city Fire Marshal David Allen told CNN.
Accelerant-sniffing dogs were aiding the investigation, officials said.
"We have determined the fire originated outside the building, but haven't determined the exact cause," said Deborah Cox, spokeswoman for the Florida state fire marshal's office.
Allen said the building had been empty for about 13 hours before the blaze was set.
Agents from the FBI and the federal Bureau of Alcohol, Tobacco, Firearms and Explosives have joined local authorities in the investigation into the fire at the American Family Planning clinic, Cox said.
Calling the fire suspicious "would be an understatement," Pensacola Police Chief Chip Simmons told the Pensacola News-Journal newspaper on Monday. The blaze was reported just before 1 a.m. Sunday.
Investigators discovered an ankle-high pile of dried leaves and shrubs in the back of the clinic that are thought to have helped spread the fire, CNN affiliate WEAR reported. No one was injured.
While authorities have not said the fire was deliberately set, the station said, many in the community have no doubt.
"Obviously somebody doesn't like abortion," resident Danielle Moulden told WEAR. "I'm against it myself, but I'd never go that far."
Pensacola has a long history of abortion-related violence, including two bombings and a fatal shooting at the clinic where the fire broke out Sunday.
In 1984, the clinic -- then known as The Ladies Center -- was bombed twice. A pipe bomb destroyed the building on June 25, 1984, and on Christmas Day that year, the clinic and two other doctor's offices where abortions were performed were bombed. Four people were convicted in the Christmas bombing, and charges were dropped in the June incident, according to WEAR.
In July 1994, Dr. John Britton and his escort, James Barrett, were shot and killed outside The Ladies Center. Barrett's wife was wounded. Anti-abortion activist Paul Hill was executed for the deaths in 2003.
In another unusual twist, the News-Journal reported the Pensacola clinic is linked to a New Jersey doctor who is facing murder charges in Maryland relating to abortions performed on late-term fetuses that were viable.
According to the website of the Florida Agency for Health Care Administration, the mailing address for American Family Planning is listed as being in Voorhees, New Jersey.
That address -- the location of American Women's Services, a second clinic -- matches that used online by Dr. Steven Brigham.
Brigham and another doctor, Nicola Riley, were charged last month with five counts each of first-degree murder, five of second-degree murder and one of conspiracy to commit first-degree murder.
Authorities said that investigation began in August, when Riley brought a woman into an Elkton, Maryland, hospital for a "complication resulting from a medical procedure," police said. Investigators later determined the woman had driven from New Jersey to Maryland for an abortion. Elkton police said several fetuses were found in a freezer chest at the clinic where Brigham and Riley worked.
CNN's Joe Sutton contributed to this report.